Effect of thermal processing on toxic heavy metals in edible seaweeds of Gulf of Mannar and their health risk assessment

Overview

Sundhar et al. measured Be, Cr, Ni, As, Se, Cd, Hg, and Pb in three edible seaweeds from the Gulf of Mannar before and after household-style thermal processing. The paper reports total arsenic and total mercury only; it does not speciate inorganic arsenic, methylmercury, or Cr(VI). Values are reported as mg/kg; the source collected and processed fresh seaweed and does not report a dry-weight conversion.

Key numbers

Table 1 reports mean concentrations in raw, microwave-cooked (MWC), steam-cooked (SCT), and boiled seaweed in mg/kg:

Table 1 raw-sample ranges were:

The paper separately reports mass-balanced processed concentrations and processing factors in Table 2. For total arsenic, those mass-balanced processed means were:

The same table reports processing-factor and reduction estimates across all eight analytes:

Source-calculated total target hazard quotient (TTHQ) values were:

Table 4 also reports country-scenario lifetime cancer risk values for Cr, Ni, tAs, Cd, and Pb. Those values are retained here only as source-calculated exposure context; the routeable occurrence evidence is the concentration table above.

Methods (brief)

Fresh U. lactuca, C. racemosa, and K. aliverzii were hand-collected from the Gulf of Mannar and cleaned with tap and distilled water. Each species was split into four 1 kg lots: raw, boiled in a water bath at 102 +/- 2 deg C for 15 min, steam-cooked at the same temperature and time, and microwave-cooked for 10 min in a household microwave oven. Samples were homogenized, frozen at -20 deg C, digested from 100 +/- 2 mg material with 2 mL nitric acid and 1 mL hydrogen peroxide, diluted to 50 mL, and measured by ICP-MS. Calibration used multi-element standards from 0.1 to 25 ug/L; yttrium and iridium were internal standards. Reported recoveries were Be 92 +/- 4.7, Cr 97 +/- 3.2, Ni 88.9 +/- 16.3, As 96.1 +/- 7, Se 88.3 +/- 17.4, Cd 98.8 +/- 2.2, Hg 95.1 +/- 5.7, and Pb 100.2 +/- 3.5. The source reports LOD/LOQ values for As (0.11/0.22 mg/kg), Cd (0.02/0.04 mg/kg), Hg (0.08/0.16 mg/kg), and Pb (0.29/0.58 mg/kg).

Implications

This paper is routeable occurrence evidence for edible seaweed from India and processing-context evidence for boiled, steamed, and microwave-cooked seaweed matrices. The raw and processed concentration rows should stay separate because cooking changed the food mass and the paper reports both measured processed concentrations and mass-balanced processing-factor estimates. Total arsenic should not be treated as inorganic arsenic, total mercury should not be treated as methylmercury, and total chromium should not be treated as Cr(VI).

Wiki pages this source may touch

• Seaweed/kelp foods (nori, wakame, kombu, dulse — as food products)
• Seaweed
• Beryllium
• Chromium
• Nickel
• Arsenic, Total
• selenium
• Cadmium
• Mercury, Total
• Lead

Verification notes

• Identity checks before writing found no existing source page for DOI 10.1016/j.rsma.2023.102827, raw handle MFK_effect-of-thermal-processing-on-toxic-heavy-metals, or cite key sundhar2023-gulf-mannar-seaweed-metals.
• All Key numbers were rechecked against /tmp/hmi-seaweed-019.txt, extracted with pdftotext -layout. Table 1 and Table 2 were extractable; table values were copied without unit conversion.
• Units are preserved as mg/kg. The source does not explicitly label dry-weight or wet-weight basis in the table headers; because the sampling and processing sections describe fresh seaweed lots and no drying step before digestion, this page records the basis as fresh/as-processed seaweed and notes the missing explicit basis label rather than converting.
• Speciation check: As is reported as As only and is recorded as tAs; Hg is reported as Hg only and is recorded as tHg; Cr is reported as total Cr and is not treated as Cr(VI).
• The Table 2 mass-balanced values and Table 1 processed concentrations are both retained because they answer different questions: concentration as measured in processed material versus mass-balanced retention/reduction.
• Brand firewall: the paper reports species, collection region, and laboratory processing methods; no consumer brands are attached to contamination values.

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.